But next time you\u2019re stargazing<\/a>, look a bit closer and even with the naked eye, you\u2019ll start<\/span> to see that the Universe is awash with colour.<\/p>\n In the colder months, my favourite sight on a clear night is the familiar Orion constellation<\/a>, and it\u2019s within this pattern of stars that we can see a classic example of colours in the night sky.<\/p>\n Look carefully at the star Betelgeuse \u2013 Orion\u2019s right shoulder (assuming he\u2019s facing us) \u2013 and you\u2019ll notice that it has an orange-red tinge to it.<\/p>\n Compare this with the star Rigel, on Orion\u2019s left foot, and you\u2019ll see that Rigel appears much more blue-white.<\/p>\n Why is this? What causes the different colours of stars<\/a>?<\/p>\n The reason stars look different colours \u2013 some are red, some are blue \u2013 is all to do with their temperatures<\/span>.<\/p>\n It\u2019s the opposite to what you might think: red stars like Betelgeuse are actually cooler than blue stars like Rigel.<\/p>\n I say cooler, but bear in mind that the surface temperature of Betelgeuse is still around 3,200\u00ba<\/span>C, compared to Rigel\u2019s 10,700\u00ba<\/span>C.<\/p>\n The colour of stars may seem counterintuitive based on our everyday experiences of linking colour to temperature (think colour-coding on taps: red for hot and blue for cold) but it\u2019s the same principle as when metal is heated in a forge.<\/p>\n First you\u2019ll see it start to glow red, then as its temperature increases the metal glows a blue-white.<\/p>\n A pair of binoculars or a telescope can reveal even more colour in the night sky.<\/p>\n Sticking with Orion, a small telescope will reveal that the fuzzy \u2018star\u2019 in the middle of his sword is not a star at all, but actually the Orion Nebula<\/a>, a region where new stars are being born.<\/p>\n Here the gas is being lit up by radiation from the young, newly formed stars, transferring energy to the atoms in the gas and \u2018exciting\u2019 them.<\/p>\n Due to the different atomic structures of the elements in the Orion Nebula, we see different colours when we look at it through a telescope, including pinky-red from hydrogen <\/span>and green from oxygen.<\/p>\n In fact, every element in the periodic table will emit a unique pattern of colours when excited, and this is the element\u2019s spectrum.<\/p>\n In the same way as you can split white light up into a rainbow using a prism, splitting observed light up into its spectrum with a technique called spectroscopy<\/a> allows astronomers to identify what elements are present within a nebula<\/a>.<\/p>\n One of the pioneers of this field of work was Margaret Huggins, an unsung hero of astronomy, who worked with her husband William in the late 19th century to catalogue the spectra of stars<\/a>, galaxies<\/a> and nebulae.<\/p>\n Today, spectroscopy is perhaps the most powerful tool in an astrophysicist\u2019s toolkit, enabling us to do everything from detecting exoplanets<\/a> around distant stars, to measuring the expansion of the Universe, to inferring the existence of mysterious dark matter<\/a> in galaxies.<\/p>\n All this from analysis of the colours in the night sky.<\/p>\n This article originally appeared in the February 2018 issue of <\/strong><\/em>BBC Sky at Night Magazine<\/strong>.<\/strong><\/em><\/p><\/body><\/html>\n By Jen Gupta Published: Wednesday, 30 March 2022 at 12:00 am Take a quick glance up at the night sky and you can be forgiven for thinking that it only exists in black and white, with distant stars appearing as pinpricks of white light against a dark background. But next time you\u2019re stargazing, look a […]<\/p>\n","protected":false},"author":24,"featured_media":30778,"template":"","categories":[1],"acf":{"readingTimeMinutes":"3"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue.jpg",1080,1080,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue-300x300.jpg",300,300,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue-768x768.jpg",768,768,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue-1024x1024.jpg",800,800,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue.jpg",1080,1080,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/why-are-some-stars-red-and-some-stars-blue.jpg",1080,1080,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"By Jen Gupta Published: Wednesday, 30 March 2022 at 12:00 am Take a quick glance up at the night sky and you can be forgiven for thinking that it only exists in black and white, with distant stars appearing as pinpricks of white light against a dark background. But next time you\u2019re stargazing, look a…","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/30777"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/30778"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=30777"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=30777"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"""\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2021\/04\/stars-448a579.jpeg?quality=90&resize=620%2C313"\" "\\"\"\"\\"\/")
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<\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/source><\/picture><\/div>The chemistry behind stars\u2019 colours<\/strong><\/h2>\n
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